Swapnote/Nintendo Letter Box is still compelling many 3DS owners to open their console every day to see what's new, and Nintendo president Satoru Iwata has hinted that there may be more to come from the app in the future.

Speaking to investors, Iwata revealed that over 10 million notes were exchanged within four weeks of the app becoming available, but acknowledged the software could grow in popularity:

And, I believe that the number of handwritten notes to be exchanged will increase at an accelerated pace if we can have users continue to enjoy the software for a long time. In fact, we have some plans to encourage more people to use it, and you will find out what I am talking about when we reveal such plans in the future. Therefore, we believe this software will gain more popularity going forward.

Iwata also may be hinting at an upcoming promotion, perhaps along the lines of the Zelda Flipnote campaign, or something else entirely. He's cagey, that Iwata.

What upgrades would you like to see made to Swapnote? If you've stopped using it, what would entice you back?